The Poisoned River Part 1.Tantor returns from the nearby river suffering from some sort of poison. After analyzing it, Professor Porter concludes that it must have come from the river, and so Tarzan and his friends convince Dumont to allow them to borrow his boat, as the poison will affect trade and jungle life. Terk stays behind with Tantor, while the others travel upriver, only to have their boat blown up by pressure caused by hippos. Going ahead, Tarzan encounters Basuli, son of Chief Keewazi of the Waziri tribe, who say that men dressed like Jane and the Professor dug in the mountainside. Meanwhile, Tantor has somehow gotten better and with Terk goes after his friends; Basuli shows Tarzan a mysterious cave shaped like a skull head.